Process for inhibiting breakdown in heated cooking oils



United States Patent 3,284,213 PROCESS FOR INHIBITING BREAKDOWN INHEATED COOKING OILS Leon A. Van Akkeren, Lombard, Ill., assignor toArmour and Company, Chicago, Ill., a corporation of Delaware No Drawing.Filed Sept. 16, 1963, Ser. No. 309,338 1 Claim. (Cl. 99-118) Thisinvention relates .to a process for inhibiting breakdown in heatedcooking oils, and more particularly to the treating of vegetable andanimal triglyceride oils to reduce polymer formation therein, forreducing foaming, and for increasing the useful life of the cookingoils.

Cooking oils, as, for example, deep fat frying oils, are subject tofoaming by reason of polymer formation therein. Further, polymerformation in the heated oils re sults in the formation of objectionablecolor so that the oil is frequently discarded.

An object of the present invention is to provide process steps forovercoming the above-described defects in heated oils and for inhibitingthe breakdown in such oils when the same are heated, as in cooking. Afurther object is to provide a method for reducing polymer formation andthereby foaming when the cooking oils are heated. Other specific objectsand advantages will appear as the specification proceeds.

In one embodiment of my invention, phosphoric acid is dispersed in acooking oil, such as a vegetable or animal oil, and the oil is thenheated slowly to a temperature of about 100 C. Acid bleaching clay isthen suspended in the oil and the temperature raised to about 120 C. andheld at 120 C. for 20 minutes. After cooling and filtering the product,the oil is subjected to any suitable procedure for the removal ofundesirable impurities. I prefer to subject the oil to heating attemperatures in the neighborhood of 220-225 C. and under reducedpressure for the removal of volatile compounds and to preventdiscoloration of the oil. The resulting product has a substantialreduction in polymer content, compared toan untreated sample of the oil.During heating, as in the cooking operation, color formation in thetreated sample is less than in an untreated sample, foaming is reduced,and the oil has a long useful life.

In the treating operation, it is important that agitation be slowerafter the phosphoric acid is added because rapid I agitation will causethe formation of free acid in the oil.

By slow or gentle stirring, effective treatment of the oil is broughtabout without the formation of free acid.

It is important that ail phosphoric acid be removed from the treated oilbefore the final high heating stage at 220-225 C., and for removal Iemploy an acid bleaching clay. The acid bleaching clay is particularlyeffective for removing any phosphoric acid or phosphate in the oil, andthere is, therefore, no tendency for the oil to darken when subjected tothe high temperature range of 220-225 C.

The phosphoric acid may be added at variable levels. I prefer to useabout 0.05 to 3.5 weight percent of concentrated phosphoric acid basedon the weight of the oil. As a specific example, I have found thatoptimum results are obtained through the use of 0.25 percent of 85percent phosphoric acid (v./w.). With 100 grams of oil, A of a mi. of 85percent phosphoric acid was used and excellent results were obtained, asdescribed in Example I.

The acid bleaching clay under temperatures of 100- 130 C., andpreferably about 120 C., is extremely effective in removing allphosphoric acid material from the treated oil, with the result that inthe subsequent high heating of 220225 C. there is no discoloration ordarkening of the treated oil. The oil containing the bleaching clay ispreferably held for 15 to 30 minutes at the selected higher temperature,and then cooled and filtered so that the phosphoric acid and reactionproducts are effectively removed.

Specific examples illustrative of the process may be set out as follows:

Example I 0.25 percent of percent phosphoric acid (v./w.) was dispersedinto refined, unbleached, undeodorized cottonseed oil by rapid stirring,after which the product was heated with gentle stirring to C. One-halfpercent of acid bleaching clay (Super Filtrol) was suspended in the oil,and the temperature raised to C. and held for 20 minutes. The productwas cooled and filtered, after which it was heated for 2 hours at220-225 C., using less than one-half mm. pressure.

The product was found to have about 25 percent reduction in polymercontent as compared with an untreated sample. When used in a deep fatfryer, there was substantially no foaming and no discoloration.

Example II A cottonseed oil sample treated with H PO was heated at -195C. for 96 hours (with stirring), and a similar sample of cottonseed oilnot treated with H PO was similarly heated at 185195 C. for 96 hours(with stirring). The treated oil gave a 24 percent reduction in polymercontent compared to the untreated sample.

Example III TABLE 1 Heating Time in Hours 0 48 96 Sample Polymer contentof tallow 1. Untreated 2. H PO4 treated While in the foregoingspecification I have set forth steps of procedure in considerable detailfor the purpose of illustrating embodiments of the invention, it will beunderstood that such detail or details may be varied widely by thoseskilled in the art without departing from the spirit of my invention.

I claim:

In a process for treating heated triglyceride cooking oils to inhibitbreakdown during heating and to prevent foaming, the steps of addingabout 0.05 to 3.5 percent of concentrated phosphoric acid to the oil,heating the oil slowly to a temperature of about 100 C. while stirringslowly to prevent the formation of free acid in the oil, addingbleaching clay to the oil When the same has reached about 100 C. and"heating the mixture to about 120 C. for about 15-30 minutes, coolingand filtering the oil to remove the clay and phosphoric acid material,and then heating the oil filtrate to about 220225 C. under reducedpressure.

References Cited by the Examiner UNITED STATES PATENTS 1,982,907 12/1934Eckey 99-163 4 FOREIGN PATENTS 326,539 3/1930 Great Britain. 377,3367/1932 Great Britain.

5 OTHER REFERENCES Andersen: Refining Oils and Fats for Edible Purposes,Pergamon Press, N.Y., 2nd ed., 1962, pp. 158 and 159.

A. LOUIS MONACELL, Primary Examiner. 1O MAURICE W. GREENSTEIN, AssistantExaminer.

